Question: 5 markers cost $8.65. Which equation would help determine the cost of 8 markers?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 5 markers. We want to know the cost of 8 markers. We can write the numbers of markers as a proportion: $\dfrac{5}{8}$ We know 5 markers costs $8.65. We can let $x$ represent the unknown cost of 8 markers. The proportion of these costs can be expressed as: $\dfrac{\$8.65}{x}$ The cost changes along with the number of markers purchased, and so the two proportions are equivalent. $\dfrac{5}{8} = \dfrac{\$8.65}{x}$